Is Sasin the only choice that makes sense? Any other close competitor? Any info on the job market as an English speaker would also be appreciated.

There are a few accredited options: https://find-mba.com/schools/asia/thailand?accredition=true&sort=popularity&numberperpage=12 Thammasat also has a well-designed programme. 

Sasin, isn't the only business school in Chula. Maybe check out Chulalongkorn Business School (CBS) https://www.chula.ac.th/program/business-administration-mba/  

AIT and Thammasat are considered to have the best MBAs in Thailand, besides Chula/Sasin. AIT has been holding the record for the #1 MBA in Thailand for a few years, according to QS MBA Rankings.

[Edited by Thant Htet Sint on Jun 29, 2023]

Thanks for your replies! AIT looks like a solid option for sure. I'll check the others out in detail.