Do I need to extend my visa due to a flight cancellation caused by the Middle East war?

Yes you can extended your visa for the reasons you have stated.

Why not apply for an extension at immigration? You're on a DTV?

Thailand’s Immigration Bureau announced special provisions starting early March 2026 (effective for permissions expiring on or after February 28, 2026) for foreign nationals unable to depart due to airspace closures, flight cancellations, and related issues from the regional crisis. The key points that apply directly to your situation:

• Overstay fines are waived for those who overstay solely because of these disruptions and who intend to depart Thailand (e.g., at the airport exit immigration). Normally, Thailand charges 500 THB per day for overstays, but this penalty is fully exempted in eligible cases—no payment required when you leave on your March 20 flight

Keep your proof of canceled flight, try and get a letter from your embassy and take that to immigration to get an extension. If that doesn't work out you can just overstay for the week (not the best solution) but the fine will be waived due to circumstances.

You got a certain amount of days to stay in Thailand stamped in your passport at entry.

You agreed to leave or apply for an Extension of Stay BEFORE that date.

Now you want to stay longer, as the airlines do not fly to your destination, and you want to cancel your agreement with Immigration, WHY?

Visit an Immigration and apply for an Extension of Stay, as it seems on your profile you work in Doha, contact the Doha Embassy and get a letter for Immigration so you can apply for the 30 day Extension of Stay as described by Immigration.

There is time enough to take action to AVOID overstay.