Update 11.02.2014: first thing after coming back from visa run, go back to Thai Best Massage. Arrive 15:40, S is not sitting outside, ask the boys: he will/might come in at 4 pm. Stroll along Silom, back 4:05 pm, ask manager: sometimes comes in late, try again at 5 or 6. Too late, come back another day, go elsewhere (Playboy massage, different story).
Update 15.02.2014: go to Thai Best in the evening, S not in. Ask manager: he is home (i.e. went back to his home province?), they don't know when he will be back. Ask for phone number, I will call him some day to inquire directly.