What does it mean to sign black and red for Thai conscription?

The conscription system in Thailand draws a red sign for military service and a black sign for exemption from service.

Due to the shortage of soldiers, Thailand has adopted the only conscription system in the world in order to recruit enough soldiers. In other words, men over 2 1 year-old must take part in a lottery conscription activity, which means that they will serve in the same year without extension, even monks and transvestites are no exception.

The Thai Constitution stipulates that everyone has the obligation to perform military service according to law. According to this regulation, all citizens who have reached the age of military service, including transsexuals, must go to military service registration and report to the conscription unit. /kloc-Men aged 0/8-30 must serve in active service according to law.