我想參加綱球公會

HKTA has, by ITF.
Another is USPTA by some USPTA coach in HK
ITF has 4 levels (Mini-tennis, then Level 1 is easier to level 3) usually for Europe
USPTA has 4 levels (Development coach, Professional 3 is easier to Pro 1) forUSA

ITF has to enrol the course one by one, but you can only enrol the USPTA exam and the level is depend on your result.

Both can be HKTA coach, but HKTA liscensed coach have to pay annual fee and earn point for continuing HKTA liscense, USPTA just pay annual fee for liscense.

HKTA 只會認可 ITF license and USPTA (因為有幾位高層只有 USPTA license ). But HKTA 不會用 USPTA coaches. HKTA-ITF coach 可以教 HKTA course.

HKTA License and USPTA license 每年都收年費, 但HKTA License 要每兩年計分,唔夠分無得續 license.
USPTA 有online coaching education and 移民可有分計(only Pro 1).
HKTA coaches have Dunlop racquets sponsor, USPTA has Head racquets sponsor (USA co.)
If you just want 教練牌, take USPTA. If you want 教 HKTA course, take HKTA- ITF.