I have some of the Irregular Siamese/Khmer - they are not small, and the round base that they stand on is on the large size. I am not sure how you would go trying to squeeze their foot onto a solid foot (40mmx15mm base) - fortunately the South East Asian armies are not replete with that type of solid foot.
I can say that the Irregular figures mix well with Outpost Khmer and with Khurusan Siamese.
Because it has my troops all over it. THAT makes it MINE!!!!
I have used Irregular to build most of my armies using their 28mm, 20mm, 15mm, 10mm, 6mm and 2mm ranges. I have been pleased with all of them. Their 28mm ECW range mix very well with Warlord figures, especially the infantry. Their 20mm Napoleonics go well with Airfix Napoleonics. The other size ranges I have not mixed with other makers.
I have always found these figures paint up really well. Ian Kaye is very obliging and helpful. Orders arrive promptly.
On one occasion I ordered 20mm Early Imperial Roman and Ancient British DBA armies. They failed to arrive. Ian immediately dispatched a further two armies which arrived safely. Investigations Ian made with the post office revealed the figures arrived at a Post Office in the Doncaster area (I am in Norfolk) then vanished. I filled a form out confirming their non arrival and I believe Ian was compensated.
He has also adapted army orders to my specification.
I personally would recommend Irregular. Good price, good service, good figures.
I have purchased Ancients, Medieval, ECW, and Napoleonic from them so cannot give an opinion on their far eastern range.
"I would rather have a russet coated Captain who knows what he fights for and loves what he knows. Than he who calls himself a gentleman, and is but little else." Oliver Cromwell