Apple Pay is a new feature which came
with the introduction of iOS 10. Apple Pay makes secure purchases
in stores, in apps, and on the web too. That is you can easily
pay with your debit cards and credit cards with just a touch using Safari.  
You can turn off  Apple Pay function in Safari on iPhone/iPad whenever you want to disable this feature because some might misuse and spend too much money buying from Apple Pay using Safari
With Apple Pay you can make payments or purchase apps including apps on Apple Watch from
your iPhone, iPad, and Mac in a safer way and faster from Safari with one Touch ID. The process
of turning on and off Apple Pay in Safari is so quick and simple. But you can turn off  Apple Pay function in Safari on iPhone/iPad whenever you want to disable this
feature because some might misuse and spend too much money buying from Apple
Pay using Safari.
How to Disable Apple Pay in Safari 
Step 1: Open the Settings app .
You can turn off  Apple Pay function in Safari on iPhone/iPad whenever you want to disable this feature because some might misuse and spend too much money buying from Apple Pay using Safari

Step 2: Scroll down and Select Safari.
You can turn off  Apple Pay function in Safari on iPhone/iPad whenever you want to disable this feature because some might misuse and spend too much money buying from Apple Pay using Safari

Step 3: Toggle Off Check for Apple Pay.
That’s it. Now you won’t be able to use
Apple Pay in Safari anymore.
Similarly, if you want to enable Apple
Pay in Safari then make sure to go with the same process above and Turn ON the
toggle Check for Apple Pay.