Samsung Galaxy S3 I9300T Jelly Bean update is now available for download. You can get the I9300TDUEMA1 4.1.2 Android JB for Galaxy S3 and install it manually. The update was released for Thailand devices and can be installed on I9300T device of yours. Here are the details:
How to Manually Install I9300T DUEMA1 Update
Download the firmware: I9300TDUEMA1_I9300TTHLEMA1_THL.zip
Follow the step by step guide: How to Flash a ROM using ODIN.
Please note this this is the official stock Jelly Bean update for Galaxy S3 I9300T. Installing this will unroot your device and you will have till a tool with ability to root I9300TDUEMA1 becomes available. We’ll keep you updated on this. Stay tuned!