Prices go crazy like that when certain airlines are not available and the only way to complete a 1 stop trip is to put two airlines together that don't belong to the same group.
This looks like a scam. Facebook page was created a few months ago. They say based in Bangkok yet the phone number is South Africa area code. No SSL certificate on the website. Looks like the website took 5 mins to make. This is not a reputable agency. PLEASE DO NOT send your signature to them. Find a proper agency with a track record. Many FB groups for teachers in Thailand and other Asian countries. Get recommendations.
This looks like a scam. Facebook page was created a few months ago. They say based in Bangkok yet the phone number is South Africa area code. No SSL certificate on the website. Looks like the website took 5 mins to make. This is not a reputable agency. Do not send your signature to them.