Maybe someone on this forum can help me. Next Saturday I am flying LHR-BKK. I arrive on Sunday morning but will fly out late the same night to Sri Lanka (CMB). I have my flight to Colombo booked already. I have over 12 hours in Bangkok and spend much of my life in Thailand. I will be dropping some luggage in Bangkok before going back to the airport for my late night flight.

After a week or two in Sri Lanka my plan is to fly back direct CMB-BKK where I will spend the next two or three months.

As i'm currently in UK it is far easier and cheaper to get a two month tourist visa from the Thai embassy in London placed in my passport before I get to immigration at Bangkok. However, I do not want immigration to stamp my two month visa when I go into BKK for 12 hours. Should I show them a print out of my ticket to Sri Lanka for later that day so I just get the normal stamp in my passport. I really don't want the immigration official stamping my two month visa for a 12 hour visit.

In short I want to preserve my two month visa for when I fly back into Bangkok after my trip to Sri Lanka. How do I go about doing this? Please advise.