Hello all, this is more belated info still, and I'm not sure the OP is still reading this. Times have changed. I'm only familiar with certain hospitals in BKK for psoriasis treatment. Bumrungrad now has phototherapy but it's expensive.
Chulalongkorn (sign up for a hospital number in the lobby G floor at the central info booth area and fill out a form and get your photo taken) has it. Phototherapy there costs about 200 baht per session ($6+), there's no one in front of you in line, in and out in about 5 minutes, one person dedicated staff, a quick walk from the Saladaeng BTS station on an overhead roofed walk deck.
I know that as recently as last fall - October - Chula offered 2 biologics to treat psoriasis. One was Cosentyx. I can't remember the other but it began with an S - so maybe Scapho but maybe Siliq. One was about $400/mo and the other about $800/mo. Bumrungrad offered biologics but at far, far higher prices. I don't know if biosimilars have arrived since then.
The in between steps at Chula are more complicated. You need a doctor to authorize the phototherapy and biologics. You can get a private appointment once you have an HN, but you have to go there to make it since they never answer their phone ever ever ever, and they will try and talk you out of a private appointment and make it months away. That runs about 1600 baht.
What they prefer you do is show up for a dermatology clinic. I've avoided this but I believe you have to get in line at 5 am. and wait all day for your number to be called - in Thai. Enormous waiting rooms. No one is remotely helpful.
Methotrexate pills are available at most pharmacies near hospitals OTC for pennies. Literally pennies, no Rx needed. Recommended dose for psoriasis tends to be around 15mg 1x weekly followed the next day by 2.5-5 mg folic acid, same drug store, even fewer pennies. I recommend tapering on and tapering off.
