Has anybody experience of trying to grow these in a tropical or sub-tropical climate? I would not ask what you might think a stupid question except that, while browsing my dictionary of Thai plant names I came across one which translates as "fragrant bean" and the Latin name of which was Lathyrus odoratus = sweet pea! This was the name from the central region of Thailand - Bangkok and its surrounding provinces. Although I am a few degrees south of Bangkok the temperatures are not really different and we are often a degree or so cooler, so if sweet peas can be grown near Bangkok we should be able to grow them here. I ask before importing expensive seeds!
Sweet peas
I would be surprised if Sweet Peas grew around Bangkok, it's a similar climate to here. It would only work if you had an abnormally cold dry season. That's more likely to happen in Bangkok than in Phuket. Most likely it's only being grown in highland areas.
I tried sweet peas, they sprouted ok, grew to about 30cm and stopped. Isaan.
A few years late lol but I live near Jakarta, Indonesia. I have two containers of snow peas/mange tout. They started growing really well and got to about 50cm. Then the leaves started to yellow from the bottom up. I planted around early Feb in the rainy season. Perhaps the average temperature of 25 Centigrade or moist soil with all the rain (they were covered under the overhanging roof but the rain would splash off the floor) caused it. It is mid March now. I will plant again in mid April when the rains should have subsided and see what happens. They had about 4 hours direct sunlight in their current position.
Have you tried clitoria ternatea? It will grow in the tropics.