I feel what Dalai Lama means by "Karma" is equal to what Thay means by "Seeds".
Dalai Lama said, "In order to reduce or eliminate the impact of previous negative karma, we need to create more forceful positive karma or accept the impact of previous negative karma without creating new negative karma."
And Thay mentioned that there are three ways to transform our deep-rooted seeds of suffering in his book titled "Understanding Our Mind" (page 155, Chapter 45 Mindfulness). The three ways are followings.
(I feel that "our deep-rooted seeds of suffering" means our past negative karma.)
1. The first way: (prophylactic treatment)
We allow seeds of suffering to lie quietly in our store consciousness while we sow new seeds and nourish existing seeds of peace, joy, and happiness.
(I feel that "we sow new seeds and nourish existing seeds of peace, joy, and happiness" means that we create our new positive karma and enjoy the impact of our past positive karma.)
2. The second way: (symptomatic treatment)
We continue to practice mindfulness that allows us to recognize seeds of suffering when they arise.
(I feel that "we recognize seeds of suffering when they arise" means that we accept the impact of our past negative karma when it arises.)
3. The third way: (aggressive approach)
We deliberately invite afflictions that have been with us since childhood in our store consciousness up into our mind consciousness and we sit down and talk with them, like old friends.
(I feel that "we deliberately invite afflictions up into our mind consciousness" means that we intentionally try to cause and accept the impact of our past negative karma.)
* The third way was not taught by Dalai Lama and its concrete method is not shown by Thay (watering unwholesome seeds in store consciousness intentionally so that afflictions may manifest in mind consciousness?). But I feel that we may be able to meet and restore communication with our wounded inner child if we are mindful and concentrated deeply and if we have deep listening capacity. Anyway we have to be very careful about the third way because Thay mentioned, "someone who is suffering greatly and does not know how to practice mindfulness should not start out practicing the third way—inviting the seeds of suffering up into the conscious mind."
Forest Light Rays in San Francisco Photo by Bo Nielsen