We went last year and rode 2 up on a 125cc Honda PCX.
We LOVED it.
So much that I sold my GS and bought a PCX in Belgium to commute.
Now on an offroad trip, but next one will be with our PCX, 2 up RTW (incl SEA).

You'll have WAY more fun in SEA on a small bike than on a big one, but the ultimate decision is yours of course. I'm just saying that I was really glad we did it on the small scooter and not a big GS, saw a guy on the GS when we were there and we felt sorry for him, us being in flipflops and t-shirt and he all dressed up.
And why do you need all the stuff for? In SEA accommodation is so cheap that there's absolutely no reason to take tent and stuff...

But that's my opinion.

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Anything over 250cc is overkill in SEA.
A 250 will power past just about anything 99% of the Locals are riding.

And you simply don't need that much power given roads and riding conditions.
I'd take less and get a smaller bike even 2 up.

Well - the locals use their mopeds for short distance commuting, going to the local market, driving to their jobs, driving their kids to school etc etc and neither can or should be compared to what a western person should want to travel around on and sitting all day on and travelling much longer distances on.

Most of the roads in Thailand and quite good all the way down those 4 digit route numbers and a bike less than 250 ccm wouldnt be able to drive at the speed of the general traffic. Especially with a lot of gear and maybe with a pillion also.

Even though I have been riding around in Northern Thailand on a Kawa KLX 250 and enjoyed it very much - it has many cons as well. The gas tank is on that model 6 liter and have a range of maybe 175 km with one person with little gear. And the seat is terrible for longer rides. (Maybe the Honda 250 are a little better....) And its very difficult, almost imposssible to find a 250 bike in Thailand for hire with panniers or even a rack to attach some gear on. I ended up buying a 40 litre backpack to use for my things when travelling and had to leave much stuff behind.

If I was going to travel 2 up on one bike in Thailand I wouldnt og for anything less than 500 ccm, maybe a 650. But if you ride one bike each a 250 is good fun if not so comfortable.

Just my opinion then. Other oeople other opinions.....

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