diff --git a/base_substate/models/__init__.py b/base_substate/models/__init__.py
index da826df400..6ac2cf86a3 100644
--- a/base_substate/models/__init__.py
+++ b/base_substate/models/__init__.py
@@ -1,3 +1,2 @@
 from . import base_substate
 from . import base_substate_mixin
-from . import mail_thread
diff --git a/base_substate/models/base_substate_mixin.py b/base_substate/models/base_substate_mixin.py
index 6b5f34d9a3..c8e6152de5 100644
--- a/base_substate/models/base_substate_mixin.py
+++ b/base_substate/models/base_substate_mixin.py
@@ -7,6 +7,7 @@
 
 class BaseSubstateMixin(models.AbstractModel):
     _name = "base.substate.mixin"
+    _inherit = "mail.thread"
     _description = "BaseSubstate Mixin"
     _state_field = "state"
 
@@ -28,6 +29,23 @@ def check_substate_id_value(self):
                     }
                 )
 
+    def _track_template(self, changes):
+        res = super()._track_template(changes)
+        first_rec = self[0]
+        if "substate_id" in changes and first_rec.substate_id.mail_template_id:
+            res["substate_id"] = (
+                first_rec.substate_id.mail_template_id,
+                {
+                    "composition_mode": "comment",
+                    "auto_delete_message": True,
+                    "subtype_id": self.env["ir.model.data"]._xmlid_to_res_id(
+                        "mail.mt_note"
+                    ),
+                    "email_layout_xmlid": "mail.mail_notification_light",
+                },
+            )
+        return res
+
     def _get_default_substate_id(self, state_val=False):
         """Gives default substate_id"""
         search_domain = self._get_default_substate_domain(state_val)
diff --git a/base_substate/models/mail_thread.py b/base_substate/models/mail_thread.py
deleted file mode 100644
index 017a9bb4cc..0000000000
--- a/base_substate/models/mail_thread.py
+++ /dev/null
@@ -1,25 +0,0 @@
-# Copyright 2023 Ecosoft Co., Ltd. (http://ecosoft.co.th)
-# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
-
-from odoo import models
-
-
-class MailThread(models.AbstractModel):
-    _inherit = "mail.thread"
-
-    def _track_template(self, changes):
-        res = super()._track_template(changes)
-        first_rec = self[0]
-        if "substate_id" in changes and first_rec.substate_id.mail_template_id:
-            res["substate_id"] = (
-                first_rec.substate_id.mail_template_id,
-                {
-                    "composition_mode": "comment",
-                    "auto_delete_message": True,
-                    "subtype_id": self.env["ir.model.data"]._xmlid_to_res_id(
-                        "mail.mt_note"
-                    ),
-                    "email_layout_xmlid": "mail.mail_notification_light",
-                },
-            )
-        return res
diff --git a/base_substate/tests/sale_test.py b/base_substate/tests/sale_test.py
index 85f05829ad..4f21c0498f 100644
--- a/base_substate/tests/sale_test.py
+++ b/base_substate/tests/sale_test.py
@@ -7,7 +7,7 @@
 
 class SaleTest(models.Model, TestMixin):
     _name = "base.substate.test.sale"
-    _inherit = ["mail.thread", "base.substate.mixin"]
+    _inherit = ["base.substate.mixin"]
     _description = "Base substate Test Model"
 
     name = fields.Char(required=True)