Anyone know what documents are needed to obtain a Thai Tax ID number? Any advice/info from people who have obtained one would be appreciated.

Is that a 10 digit number? I think I have one at the top of my annual pay/tax statement. I didn't have to do anything to apply for it, though, I just got it through my employer when I started working. Do you have a job? If so, I'd ask someone from HR.

You need a Thai work permit before you can register for a tax number. Your employer or your accountant will take care of that.

For a personal tax number; i agree you probably need a work permit but if you have your own business as part of a company or partnership then the business will be issued with the tax ID number.

I think i was issued one at the city hall, at a similar time as registering the business name.

but who can earn enough here to pay tax....certainly not me

I can.

Takes all kinds of complicated constructions to reduce it.

I have one, and it was obtained for me by a Thai friend of a farang friend of mine from my gym.

I don't have a work permit, nor do I own a business or property here. It is a 10 digit number: 1-2345-6789-0 (example).

All that was required was my passport facepage copy, current visa extension and certain other pertinent data- residence address, occupation in Thailand (for me it was "Investor").

Here's a snap of the BACK of the document; just so you know I'm not bee-essing. Not showing the front for obvious reasons.

It's handy if you want to run a business here, or need to file Thai taxes and claim deductions, or claim refunds for interest withholdings on bank accounts if you're a farang exempt from Thai tax, etc.