Can my friend extend his 45-day visa exemption in Thailand for another 30 days, and what documents are needed, including TM30 from Airbnb?

>s it possible to extend the visa for 30 days in immigration?

Yes he can

>What are the documents required?

Different immigration offices have different requirements, but all require the following:

1. Your passport and:

a. a copy of your data ("picture") page

b. a copy of your most recent visa (if you have one)

c. a copy of your most recent stamp

d. a copy of your departure card

2. MAYBE A TM30, filed in the immigration office.

3. The forms (each immigration office may have different forms, and want to use their special forms)

4. 2x passport pictures

5. 1,900 THB.

>And he is staying in Airbnb so how to get the TM30?

The property owner should file the TM30. Remember though, technically short term AirBnB rentals are illegal in Thailand, and a lease/ contract must be signed that's longer then 30 days.