Leicester City defender Thatcher has represented England at Under-21 level but is set to earn full international honours with Wales.
Thatcher qualifies for Wales courtesy of his grandmother and could gain his first cap in the Millennium Stadium tussle against Scotland on February 18.
Wales coach Mark Hughes admits he had no qualms in selecting Thatcher, despite the full back not being born in the country.
"Ben is committed to this new change in his career," said Hughes. "His agent contacted me to make me aware of his qualification and I am delighted to have him on board.
"We need as many Premiership players as possible.
"I have no problems with what people call a tradesman's entry to our squad. Fifa have allowed this one-year chance for players to change and I have played with the likes of John Robinson and Eric Young - neither of whom were Welsh - but you could not have found more committed players."
Hughes has also ignored the pleas of Newcastle United manager Sir Bobby Robson by including Craig Bellamy in his party for the Scotland clash.
Bellamy has only just returned to action after a knee injury and Robson was keen for the striker to be omitted from the friendly but Hughes has named the player in his 26-man squad.
Squad:
Coyne (Leicester), Jones (Wolves), Ward (Nott'm Forest), Crossley (Fulham); Melville (West Ham), Delaney, Edwards (Aston Villa), Gabbidon (Cardiff), Page (Sheffield United), Thatcher (Leicester), Williams (Reading), Barnard (Grimsby); Pembridge (Fulham), Davies (Tottenham), Johnson, Koumas (West Brom), Giggs (Manchester United), Oster (Sunderland), Savage (Birmingham), Robinson (Portsmouth), Speed (Newcastle); Blake (Wolves), Bellamy (Newcastle), Hartson (Celtic), Taylor (Nott'm Forest), Earnshaw (Cardiff).
