The rust killer is easy. Available in Home Works etc.maybe even Tesco. The liquid tank sealant I don't know. Matt at TYGA PERFORMANCE says he has seen tank sealer in Thailand but can't recal exactly where. He thinks it was True Value in Chonburi.
Or http://www.hotelcomfortstay.com/index_f ... ge2132.htm but it's not cheap.
Thanks for all the help on the tank sealant, the Thai mechanic freind of mine says you cannot get such a thing in Thailand (as they always say) but I will take a look today.
I have decided to operate on the tank instead by cutting it open about 2 inch from the bottom, curing the rust and re-welding the inside seams then welding the whole thing back together. This may seem a bit drastic but the tank is from a late 80's Honda Clubman 400cc, so a replacement tank would be difficult to get hold of.
A quick tip - make sure you empty the petrol out the tank before you weld it 
Many years ago I put a TY50 petrol tank on a fire to burn all the old paint off, works a treat but could cause buckling I guess. I was telling someone about this and they looked at me like I was mad, it didn't seem to enter their head that I'd make sure the tank was empty before putting it on the fire.
Don't worry the tank will be empty of petrol..lol the best way to make sure of that is when you think it's empty, hook it up to a car exhaust for a few minutes just to make sure. Klaus the rims are 2.15x18 front and 2.50x18 rear. There are a few Clubmans appearing in Thailand now from Japan at good prices, I have had mine just over a year and I just love the ride and the sound of the single cylinder engine. I hope to save some more spare cash up to buy another one someday.
In car restoration circles the greatest rust paint is called POR-15.
They also make a tank sealer, or complete MC tank kit that includes the stripper, metal prep, patching sytem, and sealer. Great stuff and their local rep is Renue International - K. Zen in BKK at 082 248 3519
Some very nice pics on the site mentioned above.The only difference between the Jap and Western models of the Clubman was the c.c with the Jap ones 400c.c compared to the European 500c.c apart from that they are the same in every way.Apparently the engine is a toned down version of the old XR 600, they also produced a 250c.c version which is a bit different in appearence and a totally different looking engine. The 250'S go for 25,000 baht - 30,000 baht and the 400cc between 40,000 - 50,000 baht. There are some pics and FAQ about the Honda Clubman G.B on the Thumper.com pages.
Yep, in Japan the cut-off is 400cc; for bigger bikes you need a license which is very expensive and almost impossible to get. When I applied for a license showing my german plus an international license for cars and bikes (of all sizes) they would issue me only a bike limited to 400cc. I raised some hell since I really wanted the license for big bikes, but they gave me a very polite run-around and a restricted license.
That's the reason why there are so many bikes from Japan with 400cc, even though there are 500cc, 600cc or 650cc versions on american and european markets.