The thing about the international terminal(s) is they regularly offload mostly widebody 747's, 777's, A-340's etc etc which usually means 300-400+ weary souls each. If it's a late morning or afternoon arrival then the immigration area could potentially have 1000's of people lined up ... all bitchy as hell (and that's just the Thai immigration dudes :blackeye: ).

My usual (UAL from Seattle) flight gets me into Bangkok at around 11:30 at night and the wait line is quite subdued and speedy. My flight in April (EVA) will get me into Don Muang at 11:30 in the morning and I'm expecting a chaotic mess ... got to get my "mai bpen rai" face on.

To answer your original question ... if I had a connection coming together with this latter flight, I'd sure make certain the leeway was quite a bit longer than 50 minutes. The 4 hour wait sounds more reasonable.

Cheers ...