“Leaving this club as a grown man is a very, very proud moment.”
Tottenham are in Seoul as part of their pre-season preparations, with Son set to start and skipper the side against Newcastle in their friendly on Sunday – meaning his final appearance for the club could come in his home country.
Frank, who replaced Ange Postecoglou as head coach in June, described Son as “a true Spurs legend” and “one of the greatest players to play in the Premier League”.
“If that is the last game for Sonny, what a place to do it here in front of his home fans,” Frank said.
“It could be a beautiful ending.”
Tottenham also face Paris St-Germain in the Uefa Super Cup on 13 August, but Son may depart by then.