------- he was old,-----------he still worked very hard thou

首先,although通常放句首,though通常放句中
其次,这两个词放的位置会决定了这个句子意思的偏重不同
Although he was old,he still worked very hard.尽管他已经老了,但他依然卖力工作.
He was old,though he still worked very hard.尽管他依然卖力工作,但毕竟已经老了.