In 2003 the Cambodians rioted and burned down the Thai Embassy in Phnom Penh over some Thai actress claiming Angkor Wat was Thai (She never said it - the storey was planted by Khmer Nationalists). The Thi ambassador had to climb over the wall to escape. :-)
I found LinkedIn and Networking at Chambers of Commerce Networking events best places to look. There are some agents that will work with you but only in certain skill domain and for jobs paying over 250k THB a month. I am basically retired from corporate work now but I still get many Thailand jobs pop up weekly in LinkedIn in my domain ie PMO. There are decent jobs out here from people with the skills and experience. It shoukd also be remembered these days many Thais have the skills too in certain industries and domains.
Yes. People have been posting they got the DTV even after being blacklisted for an overstay. The length of blacklist suggests an overstay of over a year :-)
Visa on Arrival are available to many nationalities for Cambodia. You do not state which passport you hold. I used to get one online a couple of days before to avoid using a full page in my passport. PS: next time maybe try an agency. They go to quieter border crossings and everything is set up smoothly in and out of each country.