Although Hamilton and Nico Rosberg's Mercedes team has been dominant on pace all year, the Briton has non-scored in three races and had to start from the back in another two due to various calamities.
His most recent blow was a clash with Rosberg in last weekend's Belgian GP that left Hamilton with a punctured tyre. He eventually retired, while Rosberg's ultimate second place stretched the championship gap between them back to 29 points.
Button, who was Hamilton's team-mate at McLaren from 2010-12, says he is amazed at the misfortune his compatriot is enduring this year.
"I feel for Lewis, he was leading the race [at Spa]. It is unbelievable," said Button.
"I've never seen such bad luck or misjudgement on other people's part for Lewis to lose so many points over a period of races.
"It's astonishing, really. I've never seen that before, especially when you have a car that is so dominant. They should be first and second every race.
"They are losing points hand over fist. They will win the championship, but it is a lot closer than it should be."
Although Hamilton and Button did not always have a smooth relationship when teamed at McLaren, Button believes his former stablemate is handling his challenging season well.
"For me Lewis has come across really well in the media after some disappointing races," he said.
"He has definitely grown as an individual, which is good to see, and has taken it on the chin.
"Hopefully it will build his confidence for the rest of the season rather than shatter it."
BOOING 'COULD BE DEVASTATING'
Button had not doubt that Rosberg was to blame for the Spa crash, saying "I am sure Nico would look at it and say 'I don't know what was I thinking'".
The German was loudly jeered by fans when he took to the podium at the end of the - an experience Button said he would personally struggle to cope with.
"If I got booed by fans I'd be devastated," said the McLaren driver.
"I don't go out there for the fans to love me, but I go out to put on a great show, to be a good human being at the same time.
"So I would hate that situation. It would really hurt.
"Some people, maybe you could say they are stronger in that area, but for me it would be a big issue."
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