If guess you from a Western country, hence it is no problem to get TWO land border entries for 30 days in one calendar year. Prepare USD10.- new crispy note or THB500.-.
no problem if you come in together. For the record, everyone need to be legal in Thailand, either on a visa or visa exempt, just for kids below 15years there is no fine, in case you not want to leave the country.
I not want to spoil the party, but Immigration 2 is placed in a field next to Suvarbhumi airport. Furthermore I not see the Phu Nam Ron Check Point in Kanchanaburi, but they mark the inofficial Check Point at Sangklaburi, and in Chantaburi they mark only one border Check Point. Nevertheless it is nice to see the juristriction of the various Regional Offices.