If the OP's new to Thailand, I'd suggest going to the local computer market and walking around to see what's available 2nd hand (the prices he posted look like new prices).
If you're accustomed to "back home" where everything on offer is brand new and in a box, you may be in for a pleasant surprise. You can find a 2nd hand, tested and/or refurbished laptop or desktop, sometimes at a great price. Even better deals to be had on monitors and such. Easy to find a nice 24" monitor for around $50. Look for the shops that have stacks of the same kind of used stuff, because they probably got it from a company that's upgrading, and not from someone selling off their lemon.
I'd suggest going to https://www.cpubenchmark.net/ and printing out a page of the CPU speeds to make sure you're not buying an old slug. Then wander around the computer markets...