Why are South African passports no longer accepted at the Kanchanaburi border for border runs?

The South African passports have recently been disallowed for border runs at the Kanchanaburi border due to a policy change, possibly influenced by intergovernmental agreements between South Africa, Myanmar, and Thailand. Users have reported that although they managed border runs previously, regulations now state that South African passport holders can no longer bounce back in without issues at this border, with suggestions that this rule may also affect other Myanmar border crossings.