There are regular daily minibuses to Tedim from Kalaymyo, which has flights from Yangon and Mandalay (for more information on getting to Kalaymyo, go here). Buses leave early morning from Kalaymyo, the journey time is 3 to 4 hours and tickets cost K8,000. Note that bus services in northern Chin State can be restricted on Sundays due to religious observance. 

To find out more about bus travel, go to getting around Myanmar by bus.