android:minHeight android:maxHeight is important for that.
<SeekBar
android:id="@+id/pb"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:maxHeight="2dp"
android:minHeight="2dp"
android:progressDrawable="@drawable/seekbar_bg"
android:thumb="@drawable/seekbar_thumb"
android:max="100"
android:progress="50"/>
seekbar_bg.xml
<?xml version="1.0" encoding="utf-8"?>
<layer-list
xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="@android:id/background">
<shape>
<corners android:radius="3dp" />
<solid android:color="#ECF0F1" />
</shape>
</item>
<item android:id="@android:id/secondaryProgress">
<clip>
<shape>
<corners android:radius="3dp" />
<solid android:color="#C6CACE" />
</shape>
</clip>
</item>
<item android:id="@android:id/progress">
<clip>
<shape>
<corners android:radius="3dp" />
<solid android:color="#16BC5C" />
</shape>
</clip>
</item>
</layer-list>
seekbar_thumb.xml
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="oval">
<solid android:color="#16BC5C" />
<stroke
android:width="1dp"
android:color="#16BC5C" />
<size
android:height="20dp"
android:width="20dp" />
</shape>