Hi they do state on the web site which are props and which are jets. The travel agents allow 3 hours and I would say that this is right. The new airport is a big 'un and i think that it takes some time to get from international arrivals to the domestic bit. you also get free internet, drinks and nibbles in the departure at Bangkok. If we have arrived early we have be put on an earlier plane if available.
I did read somewhere that they would not accept booking for under 3 hours. so If it was me I would be looking at something past 9. You may also find that if you arrive too early that you can't get into your room so don't break your neck to get there.
oh i wish I was coming with you I would book all the flights, carry the luggage, polish your shoes......... well maybe pay some one to do it. Enjoy.

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Kiss
God laughs at people who make plans.