I found this one from a title of a manga チャンピオン太
As my understanding, it should be read just as「ふと」.
So-called i-adjectives in Modern Japanese used to end with -shi in Classical period. Some boy's names still retain those old forms, such as たかし, さとし, つよし, やすし, ひろし or ふとし (conversely, they wouldn't name their boys in Modern adjective forms like たかい, さとい, つよい etc).
There's one more thing that Japanese names often contain some "unordinary" kun'yomi of kanji that might beyond your imagination. They also derives from obsolete readings in olden times now mostly confined within personal or proper names (名乗【なの】り). For example:
たかし: 高, 喬, 崇, 貴, 隆, 尭, 敬, ...
I believe it might just be a person name. One of the readings of 太 is indeed ふとし when used as a proper name.
Look here for example.