Sharing my successful DTV extension experience at Chiang Mai Immigration (Workaction category). Took 2 visits, but I was approved for the full 6-month extension. Yes, it was a lot of documentation to provide, but I'm happy with taking this route for the 1,900THB fee over funding a border bounce. I hope this information is helpful to somebody out there!
What I Submitted:
* Passport
* TM7
* Copy of passport bio page
* Copy of visa page in passport
* Copy of entry stamp in passport
* Copy of TM30 (printout from landlord)
* Copy of 90-day report (and had to show the original)
* Bank account verification letter
* 3 months of bank statements (originally provided 6 but the officer gave 3 back to me)
* Printout of the current bank account balance (printed from my bank's website)
* Job offer letter
* Employment verification letter
* Resume
* Portfolio
* Employment agreement
* Copy of Rental Lease
* 3 months of rent payment slips
* STM.2, STM.9, STM.11 (basic acknowledgment and consent forms on Thai visa/immigration laws. provided at the office, quick to fill and sign)
Final Thoughts:
* You can apply up to 45 days before your current stamp expires. Highly recommend using that window.
* Foreign bank accounts *are* accepted, but the officer required a bank verification letter (in addition to printed statements). My bank (U.S.-based) simply provided a letter with my name, account info, and balance. That seemed to do the trick.
* Didn't apply to me, but I was told that while we must show the equivalent of ฿500K held in the same account for 30+ days, shared accounts may be asked to show ฿1M
* One officer at this branch seemed to specialize in the DTV requests. He was helpful and professional, and openly acknowledged the inconsistency in how extensions are handled across Thailand.