Most husbands took on minor wives because other women were readily available and they got tired of their first wife "going to pot and nagging them all the time," according to researchers from Ramathibodi Hospital.
They urged the civil service system to identify male officials' marital status so they couldn't fool women into becoming their minor wives.
As part of a domestic violence study, a survey was conducted from 2009 to 2010 on state officials' attitudes towards men possessing minor wives, Ronnachai Khongsakol, deputy dean of the medical school, said on Sunday.
Altogether 1,573 officials - 884 women and 689 men - were interviewed.
The main reason for philandering cited by the male respondents was opportunities and close proximity to other women at 58.2 per cent. Other reasons were getting bored with their wife due to overfamiliarity from living together for a long time (48.2 per cent), the wife's behaviour such as drinking, gambling, nagging or being aggressive (42.7 per cent) and the wife not taking care of her looks and getting fat (42 per cent).
The women said they thought men found minor wives because they were insatiable (77.8 per cent) and they were in a tempting environment surrounded by other women (73.4 per cent).
Almost 60 per cent of the men said having a minor wife was a man's personal business, while only 28.5 per cent mentioned it as an immoral act. About half of the women said it was an immoral act and 39 per cent felt it was a very personal matter.
Ronnachai also offered a suggestion that men's marital status should be identified in household registrations and as a requirement in civil service regulations to avoid such issues.