Microsoft Teams Direct Routing in Thailand: What Buyers Should Know Before Choosing a Provider

What Microsoft Teams Direct Routing actually does

Microsoft Teams includes a built-in calling capability called Teams Phone. By default, using Teams Phone for external calls requires subscribing to Microsoft's Calling Plans — which means Microsoft becomes your phone carrier.

Direct Routing is the alternative. It lets you connect Teams Phone to your own PSTN carrier using a certified Session Border Controller (SBC). In practice, this means:

• Your organization keeps its existing Thai DID numbers
• Calls to and from the PSTN go through your own SIP Trunk provider, not Microsoft's carrier
• Call costs follow your existing SIP Trunk pricing, not Microsoft's per-minute rates
• You retain control over routing, failover, and dial plan configuration

For most Thai organizations with existing phone infrastructure, Direct Routing is the more practical and cost-effective path than Microsoft Calling Plans.

Why the SBC choice matters

The Session Border Controller is the certified gateway that sits between your SIP Trunk and Microsoft Teams. Microsoft maintains a list of certified SBC vendors. Not every VoIP gateway or SIP proxy qualifies.

Ribbon is one of the vendors on Microsoft's certified SBC list. Ribbon SBCs handle the protocol translation, media relay, and security boundary between the Teams environment and the PSTN carrier. Choosing a provider that runs a certified Ribbon SBC means the interconnect between Teams and your phone network is handled by equipment that Microsoft has validated.

The alternative — using non-certified equipment or adapters — creates a support gap. If call quality degrades or calls fail to route correctly, Microsoft support will not help troubleshoot a non-certified interconnect.

What SIP Trunk quality means for Teams calls

Direct Routing passes your voice media through the SIP Trunk. The quality of calls in Teams is therefore directly affected by:

• SIP Trunk latency and jitter
• Concurrent channel capacity on the trunk
• Codec negotiation between the SBC and the Teams environment
• How the SBC handles media transcoding if codecs do not match

An organization can have a correctly configured Ribbon SBC and a licensed Teams Phone environment, and still experience poor call quality if the underlying SIP Trunk has inconsistent latency or insufficient capacity.

This is why Direct Routing deployments benefit from using the same provider for both the SBC and the SIP Trunk. When the network and the SBC are managed by the same team, troubleshooting is faster and the provider can observe both sides of the call path.

How Thai organizations typically deploy Direct Routing

There are two common deployment patterns in Thailand:

**Pattern 1: Teams only** The organization standardizes on Microsoft Teams for all communication. Direct Routing extends Teams to handle external PSTN calls. No separate PBX is required. This works well for organizations that are already running Teams as their primary collaboration platform and want to consolidate desk phones and softphones under Teams.

**Pattern 2: Teams plus Cloud PBX** The organization runs a Cloud PBX (Yeastar or 3CX) for internal call handling, advanced IVR, call queues, and call recording, while Direct Routing enables Teams users to receive and place external calls through the same PSTN connection. This is common in hybrid deployments where only part of the workforce uses Teams daily, and the contact center or reception team uses the full PBX feature set.

Both patterns require a Ribbon SBC and a qualified SIP Trunk. The difference is in which platform handles the call routing logic before and after the PSTN gateway.

What to evaluate when choosing a Direct Routing provider in Thailand

Before selecting a provider, Thai buyers should ask these questions:

**On the SBC:** - Is the SBC on Microsoft's certified list? - Is it managed by the provider, or are you responsible for SBC administration? - What is the failover configuration if the SBC is unreachable?

**On the SIP Trunk:** - Does the provider own the SIP Trunk network, or are they reselling capacity from another carrier? - Are Thai DID numbers available, and can existing numbers be ported? - What is the concurrent channel limit, and how is it scaled?

**On the team:** - Are the engineers certified on the PBX platform being deployed (Yeastar, 3CX, or others)? - Has the provider completed previous Direct Routing deployments in Thailand? - Who handles support if calls fail — and do they have access to both the SBC and the trunk?

The most common failure in Direct Routing deployments is a provider who can configure the SBC but does not manage the SIP Trunk, or vice versa. When the two components are separated across different vendors, fault isolation becomes difficult and resolution time increases.

How SIPPER approaches Direct Routing

SIPPER provides Microsoft Teams Direct Routing on a Ribbon SBC connected to SIPPER's own SIP Trunk network. The same team that manages the SBC also manages the underlying carrier connection, which means both sides of the call path are observable from a single point.

SIPPER's engineering team is certified on Yeastar (YSCE level, all 9 certification tracks) and 3CX (Advanced Certified Engineer V20). For organizations that need a Cloud PBX alongside Teams — the hybrid pattern described above — SIPPER can provide the full stack: SIP Trunk, Ribbon SBC, Direct Routing, and Cloud PBX on own IaaS infrastructure.

When Direct Routing is not the right fit

Direct Routing is not always the correct choice. Organizations that are not already running Microsoft 365 with Teams licensing, or those with a very small number of PSTN lines and no existing SIP infrastructure, may find that Teams Calling Plans or a standalone Cloud PBX without Teams integration is simpler and less expensive.

The decision depends on: - Whether the organization is standardizing on Teams as its primary collaboration platform - Whether existing PSTN numbers must be retained - Whether per-minute Microsoft Calling Plan pricing is acceptable versus SIP Trunk per-channel pricing - Whether the IT team can manage a Teams-integrated telephony environment

If any of these conditions point away from Direct Routing, a standalone Yeastar or 3CX Cloud PBX with SIP Trunk is typically the more practical path.

Summary

Microsoft Teams Direct Routing connects Teams Phone to your own PSTN carrier via a certified SBC. In Thailand, the outcome depends on the quality of the SBC (Ribbon is the recommended choice), the reliability of the underlying SIP Trunk, and whether the provider manages both.

Organizations evaluating Direct Routing should ask whether the provider owns its own network, which SBC vendor is in use, and whether their engineers are certified on the PBX platform being deployed alongside Teams.