halal food in bangkok or pattaya

The Tableeghi Markaz is almost right behind the Bangkok General Post Office. When you land in the city take the Taxi to the area of Bangkok General Post Office

1. You will see plenty of Muslims in the area (Pakistani Pathans usually) walking around Shalwar Qameez
2. Around Namaz times lots of people moving about
3. Plenty of Hotels and Resturants run by Pakistani (and some by Tableeghees) which are Halal
4. South of Thailand is run by plenty of Muslims but I guess your friend won't be going there.

There are 2 other Deobandi Musallas in the same area but around any Namaaz time you won't be able to miss people making their way to the Masjid; stop and ask anyone.

There is a very nice Hyderabadi Resturant (one street away from Markaz) whose owner is Tableeghi so its Halal.