I actually got this in Thailand first time I went there (maybe second)...a few hours before the flight home
Was extremely unpleasant.
When I got it I couldn't actually stand up. Totally disorientated, didn't know what time it was. I knew I was on walking street tho. I was very very sick, had an evil headache and I think I passed out several times. It came on very quickly. I was fine, had been down the beach all day as usual. We were walking down to grab some food and I just couldnt stand up, dizzy, like I was wasted as you described and felt very ill...and I actually was very sick.
As bad as it was for a couple of hours it was actually quite easy to fix...I drank the water out of 3 coconuts, a bottle of coke and after about an hour I felt ok again. Came out of it as quick as I went in. It was like waking up. Felt lieka new day. Very strange.
Anyway...the problem was not drinking. I have since been back to thailand 2 or 3 times and have not suffered from it again. Prevention is far better than the cure. Just drink a lot, keep hydrated and keep out the sun if you can. I am not sure if suncream has an effect but the first year I burnt really bad. So then after I have caked myself in the stuff (no joke) still got burnt one day but it was very hot. Did not have any sunstroke tho, but some evenings I felt a bit wishy washy, kinda not quite with it. I guess that could be mild sunstroke.