<?php

$arr = [
  [
    "name_TH" => "test",
    "currnetMonth" => 200.0
  ],
  [
    "name_TH" => "test2",
    "currnetMonth" => 3000.0
  ],
  [
    "name_TH" => "test3",
    "currnetMonth" => 1455.0
  ]
];

usort($arr, function ($a, $b) {
   if ($b["currnetMonth"] == $a["currnetMonth"]) return 0;
   return $b["currnetMonth"] < $a["currnetMonth"] ? -1 : 1;
});

print_r ($arr);