Phytosanitary certificate? That seems silly...
When I was growing mostly tomatoes and herbs, and only a few mainstream peppers like JalapeƱo and Anaheim, Baker Creek was a great seed source. The catalog is a work of art, the prices are quite reasonable, the seeds germinate well, and they actually have a pretty nice selection, as long as you don't need seeds for the latest, trendiest C. chinense.
My trouble started when I began obsessing around the various Thai peppers. Nobody really seems to really know what's what as far as which names go with which cultivars, or even which species some of the Thai peppers are in. I would gladly accept Dewitt and Bosland's taxonomy, but none of the seed suppliers, even those based in Thailand, seem to be aware of it...
I understand that all pepper taxonomy tends to be obfuscated and ambiguous, but Thai pepper classification seems to be especially confusing, and the seeds hard to obtain. There is one cultivar which everyone seems to agree on and which is readily available: the old standby "Thai Chile." It's one of my all-time favorites, and will always have a place in my garden.
Maybe one day someone will offer a dependable supply of clearly-indentified Thai pepper seeds, and I will finally be able to grow and eat Prik Ki Nu Suan.