I bought True "wireless broadband plus" router, which I believe is locked to their system. Two removable antennae, 2 LAN ports, up to 32 wireless users. It was on promotion for 1000 baht. Fast and easy set up, small package, fits in a briefcase.
Then got an unlimited True sim card, too expensive according to posters here, at 699/month. Should have shopped around, but I wanted it "now." Minimum 3-month contract.
Have been using it in Bangkok (5th floor condo) and rural Korat for two months, both locations dependable service 20-30 mbps.
Will cancel the sim next month when we have True fiber installed in the house. Good news. Both True and 3BBB in this area ask for a work permit for foreigner to install fiber on a yearly contract, but after a call to the main office, showing a bank passbook is sufficient.