I've entered on the 30 day exemption several times, with a return ticket over 30 days. I've never been asked to show a ticket out of Thailand within the 30 days, although I often had one for travel to Phnom Penh, Yangon etc.

Last year I also entered on a 60 day visa, with a return flight nearer to 90 days later. No one asked to see a ticket out within the 60 days. Of course, the risk remains.

Maump might also consider that land borders to Laos and possibly Cambodia are closed at present. To counter the risk of them remaining closed, £60 on a 90 day visa could be money well spent.