ยกเลิกยูทูปพรีเมี่ยม

if you subscribed via the App Store on iPhone or iPad, see:

If an app has a subscription associated with it, see -> Delete apps on your iPhone, iPad, and iPod touch -> Delete apps on your iPhone, iPad, and iPod touch - Apple Support

• If you delete an app, it doesn’t cancel in-app subscriptions that you might have. While deleting an app, you might see a Cancel Subscriptions option. Learn how to cancel your subscriptions.

If you don't want to continue a subscription you need always to cancel that subscription in time, see the following Apple articles:

If you want to cancel a subscription from Apple

If you want to cancel a subscription from Apple - Apple Support

• Go to Settings -> Ttp your Apple ID -> Ttp Subscriptions and find YouTube -> tap Cancel subscription and Confirm that you want to cancel.

If the subscription that you want to cancel is not listed

If the subscription that you want to cancel is not listed – Apple Support (UK)

If you subscribed via Google Play, you need a non-iOS device to go to the subscriptions page of the Google Play Store and cancel it.

If it is not clear , get help and assistant from Apple directly, see Contact Apple for support and service -> 

บริการช่วยเหลืออย่างเป็นทางการของ Apple

Or call -> Within Thailand: 1800 019 900